CO-EXPRESSION OF FACTOR VIII AND VON WILLEBRAND FACTOR

Description

Field of Invention

[0001] The present invention relates to the functional expression of recombinant factor VIII (rFVIII) in cells and in particular to its stable expression and excretion from cells in in vitro and/or in vivo applications.

Background to Invention

[0002] Factor VIII (FVIII) is a large, complex glycoprotein. It is synthesized as a 330-kDa protein with the domain structure A1-A2-B-A3-C1-C2 where both A and C domains have internal sequence homology and approximately 40% sequence identity to the A and C domains of factor V. The B-domain, which constitutes 38% of the total sequence, shares no sequence identity with other known proteins, including the B-domain of factor V. It is, however extensively glycosylated and contains 19 of the 26 asparagine (N)-linked glycosylation sites on the whole molecule.

[0003] Much insight into the biosynthesis of FVIII has come from the analysis of expression in heterologous cell types with the purpose of producing rFVIII for therapeutic purposes. In addition, characterisation of the molecular defects responsible for the autosomal recessive bleeding disorder associated with combined deficiency of factors V and VIII revealed the importance of intracellular trafficking in the biosynthesis of FVIII (1,2).

[0004] Early studies of rFVIII demonstrated that the B domain could be deleted without loss of FVIII procoagulant activity (reviewed in 3). Expression cassettes encoding B domain-deleted rFVIII resulted in significantly higher levels of mRNA over equivalent full-length rFVIII expression cassettes, resulting in higher levels of rFVIII protein synthesis. However, the levels of rFVIII secreted into the media did not increase proportionately, suggesting intracellular interactions were limiting efficient secretion (4). rFVIII is co-translationally translocated into the lumen of the ER where it folds and assembles into tertiary structures. These reactions are facilitated by enzymes and molecular chaperones that interact with folding intermediates of rFVIII.

[0005] In vivo, immediately after its secretion into the circulation FVIII interacts to form a tight non-covalent complex that protects it from premature clearance or inactivation by proteolysis. FVIII binds to von willebrand factor (VWF) through two sites in the A3 and C2 domains. In vitro it has been shown that the addition of VWF to the culture media or co-expression through transfection with a VWF expression cassette of cells expressing rFVIII leads to increased accumulation of rFVIII in the media by increasing the stability of the rFVIII in the culture media (6). It has been proposed that VWF promotes the dissociation of rFVIII from the cell surface and may also promote the assembly of the two chain hetero-dimer of the heavy and light chains of rFVIII (14, 15), however it is only thought to from a non-covalent complex with FVIII once outside the cell.

[0006] Deletion, of the entire B-domain which led to a 17-fold increase in mRNA and primary translation product only resulted in a 30% increase in the levels of secreted protein, suggesting that the rate of ER-Golgi transport was reduced and that levels of FVIII mRNA were not limiting expression (4). The introduction of multiple N-linked glycosylation sites known to be important in ER-Golgi transport of FVIII increased levels of secreted FVIII, suggesting that the rate of ER-Golgi transport may be a rate limiting step (7). However, a significant amount of FVIII within the ER never transits to the Golgi compartment due to a failure to fold correctly and misfolded FVIII accumulation in the ER can result in oxidative damage and apoptosis (5), suggesting that FVIII folding is the rate-limiting step in FVIII expression.

[0007] In a recent study designed to investigate the effect of FVIII expression cassettes with various B-domain constructs the effect of codon optimising these sequences for expression in Homo sapiens was also investigated (8). Human embryonic kidney cells (HEK293T) cells were transiently transduced and expression of FVIII was assessed 72h latter. Surprisingly no significant effect of incorporation of the B domain regions was observed, however a 7 to 30-fold increase in functional FVIII expression from codon optimised sequences was observed. Although protein secondary structure is determined primarily by the amino acid sequence, protein folding within the cell is affected by a range of factors: these include interaction with other proteins (chaperones) and ligands, translocation through the ER membrane and redox conditions. The rate of translation can also affect protein folding and it has been suggested that codon usage may be a mechanism to regulate translation speed and thus allow stepwise folding of individual protein domains (9,10). FVIII is a complex multi-domain protein in which non-sequential segments of the nascent polypeptide chain may interact in the three dimensional fold. Ribosome stalling at 'rare' codons may therefore lead to alternative folding pathways generating altered conformations and potentially misfolded protein. A potential explanation for the observed effect of codon optimised sequences may be that they allow efficient translation and transport across the ER membrane allowing the nascent FVIII polypeptide chain to fold correctly leading to the increased levels of secreted FVIII observed in vitro and in vivo.
Spencer et al (16) teaches the use of a Lentiviral vector platform to express a bioengineered recombinant Factor VIII at very high levels. However this is achieved by creating a chimeric FVIII sequence which still includes 12% porcine sequence and a such the FVIII is not non truly a native or human sequence. This may cause regulatory concerns with regards its use so this may not be desirable, particularly in a human context. Kaufman et al., Mol. Cell. Biol. vol.9, No.3. p.1233-1242 (March 1989) and Chen et al., Thrombosis Research vol. 95, p. 105-115 (1999) describe co-expression of recombinant FVIII and VWF in mammalian cell lines. However, they do not address the problem of improving long-term FVIII production nor do they comment on codon-optimisation.

Summary of the Invention

[0008] The present invention is based on studies performed by the inventors into B domain deleted (BDD) rFVIII expression in cells and in particular codon optimised rFVIII.

[0009] The invention is based on work carried out by the present inventors towards providing high-yield production of versions of mammalian, especially human FVIII tailored for animal and human trials and therapeutic applications, which is based on the use of codon optimised chemically synthesised genes that are transfected into, for example mammalian cells either in vitro or in vivo.

[0010] The inventors have observed that mammalian cells transfected with hamster codon optimised B domain deleted recombinant FVIII (BDDFVIII coop) did not remain viable over a period of time and that the BDDFVIII coop could not therefore be obtained stably in useful quantities. However by co-expressing BDDFVIII coop with similarly hamster codon optimised VWF, stably transfected cells could be obtained, which remain viable for a significant period of time and from which a high level of expression of BDDFVIII coop could be observed. Kaufman (6) suggests that co-expression of VWF with rFVIII leads to extra-cellular stability of rFVIII, but there was no suggestion that co-expression of VWF with BDDFVIII coop might help maintain cell viability, as well as functional viability of BDDFVIII coop.

[0011] In a first aspect there is provided a mammalian cell comprising an exogenously introduced nucleic acid which is capable of recombinantly expressing FVIII wherein the nucleic acid, or portion thereof which encodes said FVIII has been codon optimised for expression by the mammalian cell; and wherein the cell further recombinantly co-expresses von Willebrand Factor (VWF).

[0012] In accordance with the present invention the nucleic acid which expresses VWF is introduced into the mammalian cell prior to the nucleic acid which is capable of recombinantly expressing FVIII.

[0013] In a preferred embodiment the VWF polynucleotide sequence may also be codon optimized in a similar manner to the FVIII sequence. Thus, although the remainder of the specification refers to codon optimisation and expression of FVIII in particular, this is not to be construed as limiting and may extend in a similar manner to VWF.

[0014] The mammalian FVIII referred to is preferably human FVIII, but may be FVIII from another primate or other mammal, such as that from mouse, rat, hamster, rabbit, hamster, dog, horse, cow, pig, sheep, camel, cat, guinea pig, or the like. The FVIII may be a modified version as known in the art, for example a B domain deleted version of BDD FVIII.

[0015] The mammalian host cell may be any cell suitable for expression of codon optimised FVIII and may for example be of human, mouse, hamster, rat, monkey, rabbit or dog origin. Naturally the FVIII or modified version thereof will be codon optimised as known in the art and described further below so as to be suitably codon optimised for expression in the chosen cell. For example if the cell is of hamster origin the FVIII nucleic acid coding sequence will be codon optimised for hamster expression. Cell lines which may be suitable for expression include HEK 293, CHO, 3T3, BHK, MICK, Vero, Junket, Hela, as well as derivatives of such cells known in the art.

[0016] Although the nucleic acid may be codon optimised for expression in a particular mammalian cell, the amino acid sequence may conform to FVIII from the same or a different species. In a preferred embodiment the FVIII amino acid sequence corresponds to a human FVIII sequence or a fragment thereof. Suitable human or other animal FVIII fragments include in a preferred embodiment, a FVIII sequence from which the B domain has been deleted, and optionally replaced with a short B-domain spacer rich in asparagine-linked oligosaccharides. A preferred FVIII B-domain deleted amino acid sequence is shown in Figure 1. Such a sequence when codon optimised for expression in hamster, such as CHO or BHK cells is shown in Figure 2.

[0017] In certain embodiments, the present invention utilises an isolated polynucleotide comprising a nucleic acid fragment which encodes a polypeptide at least 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99% identical to the sequence shown in Figure 2, and where the nucleic acid fragment encodes or is a variant of a codon optimised FVIII, such as human FVIII represented by Figure 1. The human codon optimised coding region can be optimised by any of the methods described herein.

[0018] Typically the nucleic acid is engineered within an expression vector, which is capable of expressing said recombinant FVIII under suitable conditions.

[0019] Conveniently, the codon optimised nucleic acid sequence can initially be chemically synthesised rather than cloned and mutagenised in order to generate the necessary codon optimisation. In accordance with the present invention it is possible to produce large quantities of recombinant mammalian FVIII and its variants hitherto not possible using the previously described techniques. Typically the methods of the present invention may produce protein yields of at least 0.5 mg of recombinant FVIII (or its variants) per liter of culture medium, such as at least 1 mg, 5mg, 10 mg, 50 mg, 100 mg, 200 mg or 500 mg per litre of culture medium. It will therefore be appreciated that it is possible following the methods of the present invention, when using industrial-scale fermentors, to produce hundreds of milligrams or grams, or even kilogram-quantities of recombinant FVIII and variants thereof. It will also be further appreciated that it is possible following the methods of the present invention to achieve protein yields comparable with or greater than the productivity of industrial production cell lines for FVIII (i.e.>0.05 pg/cell/day. This may or may not require the use of gene amplification techniques such as DHFR/methotrexate).

[0020] In a further aspect the present invention provides a cell culture comprising a mammalian cell as described herein according to any preceding claim, which is capable of expressing the FVIII in an amount of ≥ 0.1pg/cell/day, typically ≥ 0.25 pg/cell/day.

[0021] The cell culture may be considered to be stable in that it comprises one or more of the following features:

1) the cell culture comprises at least 5 x 10⁶, 1 x 10⁷ or 1 x 10⁸ cells per ml;

2) a cell viability of at least 80%, 90%, 95% or 97%; and

3) cell viability is maintained for at least 2 weeks, 3 weeks or even 4 weeks.

[0022] In a further aspect there is provided a method of preparing recombinant mammalian FVIII or a B domain deleted version of FVIII, comprising providing a cell, transfecting the cell with a vector capable of recombinantly expressing VWF and thereafter further transfecting cells transfected with VWF with a vector capable of recombinantly expressing FVIII or a B domain deleted version of FVIII, wherein the transfections are carried out with vectors which comprise codon optimised nucleic acid constructs capable of expressing FVIII or a B domain deleted version of FVIII and VWF in said cell. Advantageously, the present method may not require, in some embodiments, the use of gene amplification techniques such as DHFR/methotrexate amplification methods known in the art (see for example, Kaufman (17). The inventors have observed that methotrexate at levels of up to 0.5µM mg be used to increase productivity of recombinant FVIII, but higher levels have a deleterious effect, which was unexpected.

[0023] The above process may further comprise purifying said proteins or complex from the cell and/or culture medium in which the cell is grown. Purification may typically involve the use of chromatographic methodologies, such as fast-protein liquid chromatographic or high-performance (pressure) liquid chromatographic techniques known in the art. In a subsequent purification step, crude material may, for example, be loaded onto a sepharose or agarose based affinity chromatography column, containing an affinity ligand for VWF or FVIII such as a monoclonal antibody or a peptide ligand. In a preferred embodiment an antibody to VWF (CaptureSelect VWF; Life Technologies) or FVIII (FVIIISelect; GE Healthcare) is employed in order to bind to said FVIII and/or VWF, and eluted by application of a salt gradient (e.g.1-1.5 M NaCl or CaCl₂) over multiple column volumes; in a further step, FVIII containing fractions from the previous step(s) may be loaded onto, for example, anion exchange and/or HIC columns. The order of such purification steps may be altered to increase yield and/or purity of the rFVIII or variant thereof.

[0024] Rather than conventional gene cloning and expression, the present invention is based on an initial chemical synthesis of the codon optimised DNA molecules encoding said FVIII (and variants thereof), using gene design and synthesis techniques in the art (e.g.Gene composer: database software for protein construct design, codon engineering, and gene synthesis, see Lorimer (18) for example. In this manner, the codon optimised nucleic acid is synthesised de novo prior to cloning into a suitable expression vector. Conventional site-directed mutagenesis techniques known in the art to carry out codon optimisation of the FVIII gene would be unfeasibly time-consuming, if not impossible due to the high risk of introducing additional mutational variations during the requisite repeated rounds of site-directed mutagenesis. However, site-directed mutagenesis may be used following cloning of the synthetic codon optimised FVIII, in order to accomplish one or a combination of site-specific mutations in the product.

[0025] Codon optimisation is carried out in order to enhance the expression levels of the mammalian FVIII and its variants in the desired host organism or cell type, such as hamster or hamster cells. Said optimisation involves one or more of the following: adapting codon bias to match that of the chosen host organism or indeed cell type; avoiding regions of high (>80%) or low (<30%) GC content; minimising any potential internal TATA boxes, chi-sites and ribosome-entry sites; minimising AT-rich or GC-rich stretches of sequence, avoiding repeat sequence and RNA secondary structures, minimising any (cryptic) splice-donor and/or splice-acceptor sites; and ensuring any desired restriction endonuclease sites are only found at the extreme 5' and 3' ends of the nucleic acid to facilitate cloning. Preferably all of the above considerations are taken into account when optimising the nucleic acid sequence. The skilled addressee is able to make such modifications to the original FVIII sequence based on prior knowledge in the art in relation to the codon bias of the chosen host and other teachings (e.g.Codon bias and heterologous protein expression. Gustafsson C, Govindarajan S, Minshull J. Trends Biotechnol 2004 22:346-53). Certain companies such as Geneart (Regensburg, Germany), GeneScript (Piscataway, New Jersey, USA) and DNA2.0 (Menlo Park, California, USA) provide a service for optimising and synthesising nucleic acid sequences that are tailored for expression in a specified host organism.

[0026] Expression vectors useful in the present invention include chromosomal-, episomal- and virus-derived vectors, for example vectors comprising bacterial plasmids, bacteriophages, yeast episomes, yeast chromosomal elements, viruses such as baculoviruses, papova viruses, vaccinia viruses, adenoviruses, fowl pox viruses, pseudorabies viruses and retroviruses, and vectors derived from combinations thereof, such as cosmids and phagemids.

[0027] Recombinant expression vectors may be introduced into host cells using well-known techniques such as infection, transduction, transfection, transvection, electroporation and transformation. The vector may be, for example, a phage, plasmid, viral or retroviral vector. Retroviral vectors may be replication competent or replication defective. In the latter case, viral propagation generally will occur only in complementing host cells.

[0028] The nucleic acid encoding the FVIII should be operatively linked to an appropriate promoter. Suitable eukaryotic promoters include the cytomegalovirus immediate early promoter, the herpes simplex virus thymidine kinase promoter, the early and late SV40 promoters, the promoters of retroviral long terminal repeats (LTRs), such as those of the Rous sarcoma virus and metallothionein promoters, such as the mouse metallothionein-I promoter. Synthetic promoters are also suitable.

[0029] The expression constructs will further contain sites for transcription initiation, termination and, in the transcribed region, a ribosome-binding site for translation. The coding portion of the mature transcripts expressed by the constructs will include a translation-initiating AUG at the beginning and a termination codon appropriately positioned at the end of the nucleic acid sequence to be translated. It is facile, using synthetic genes, to optimise all of these features of the insert to maximise gene-expression levels and recombinant-protein yields.

[0030] As indicated, the expression vectors will preferably include at least one selectable marker. Such markers include e.g. dihydrofolate reductase or neomycin or zeocin resistance for eukaryotic cell culture and e.g. tetracycline or ampicillin-resistance genes for culturing in E. coli and other bacteria.

[0031] As indicated, introduction of the construct into the host cell can be effected by calcium phosphate transfection, DEAE-dextran mediated transfection, cationic lipid-mediated transfection, electroporation, transduction, infection or other methods. Such methods are described in many standard laboratory manuals, such as Davis LGG et al., (21).

[0032] As indicated, transcription of the DNA encoding the polypeptides of the present invention by higher eukaryotes may be increased by inserting an enhancer sequence into the vector. Enhancers are cis-acting elements of DNA, usually from about 10 to about 300 bp that act to increase transcriptional activity of a promoter in a given host cell-type. Examples of enhancers include the SV40 enhancer, which is located on the late side of the replication origin at bp 100 to 270, the cytomegalovirus early-promoter enhancer, the polyoma enhancer on the late side of the replication origin, and adenovirus enhancers.

[0033] It will be recognised in the art that the amino-acid residue sequence of a FVIII polypeptide may be selectively varied without having a significantly detrimental effect on the structural integrity or functional properties of the protein. If such differences in sequence are contemplated, it should be remembered that there are regions of the protein that are critical to its biological activity. There will also be residues that are critical to the folding of the protein or for stabilisation of its folded structure. Some residues serve as glycosylation sites, recognised by enzymes that covalently attach glycans to, for example, Asparagine. In general, it may be possible to safely replace residues that contribute directly or indirectly to structure or function by other residues that are chemically similar (this is known as a conservative substitution). In the cases of amino-acid residues that contribute neither to structural integrity nor to functional sites, it may be possible to safely replace such a residue with an amino-acid residue of a different chemical nature (a non-conservative replacement).

[0034] Typically seen as conservative substitutions are the replacements, one for another, amongst the aliphatic amino-acids Ala, Val, Leu and Ile; interchange of the hydroxyl residues Ser and Thr; exchange of the acidic residues Asp and Glu; substitution between the amide residues Asn and Gln; exchange of the basic residues Lys and Arg; and replacements amongst the aromatic residues Phe and Tyr. Non-conservative substitutions could include substitutions with both naturally encoded amino-acid residues and a non-naturally encoded (unnatural) amino-acid residue. The unnatural amino-acid residue could be one that serves as a site-specific attachment sites for conjugation with chemical moieties (such as polyethylene glycols (PEGs) and other polymers), or with biochemical groups (such as glycans) that enhance the therapeutic efficacy of FVIII.

[0035] As indicated in detail above, further guidance concerning which amino acid changes are likely to be phenotypically silent (i.e. are not likely to have a significant deleterious effect on a function) can be found in Bowie (19).

[0036] The terms "nucleic acid" or "nucleic acid fragment" refer to any one or more nucleic acid segments, e.g., DNA or RNA fragments, present in a polynucleotide or construct. While the term "nucleic acid," as used herein, is meant to include any nucleic acid, the term "nucleic acid fragment" is used herein to specifically denote a fragment of a designed or synthetic codon optimised coding region encoding a polypeptide, or fragment, variant, or derivative thereof, which has been optimised according to the codon usage of a given species or cell type. As used herein, a "coding region" is a portion of nucleic acid that consists of codons translated into amino acids. Although a "stop codon" (TAG, TGA, or TAA) is not translated into an amino acid, it may be considered to be part of a coding region, but any flanking sequences, for example promoters, ribosome binding sites, transcriptional terminators, and the like, are not part of a coding region. Two or more nucleic acids or nucleic acid fragments of the present invention can be present in a single polynucleotide construct, e.g., on a single plasmid, or in separate polynucleotide constructs, e.g., on separate plasmids. Furthermore, any nucleic acid or nucleic acid fragment may encode a single polypeptide, or may encode more than one polypeptide, e.g., a nucleic acid may encode two or more polypeptides. In addition, a nucleic acid may encode a regulatory element such as a promoter or a transcription terminator, or may encode heterologous coding regions, e.g. specialised elements or motifs, such as a secretory signal peptide or a functional domain.

[0037] The terms "fragment," "variant," "derivative" and "analog" when referring to FVIII polypeptides of the present invention include any polypeptides which retain at least some of the functional biological activity of the corresponding native polypeptide. Fragments of FVIII polypeptides of the present invention include proteolytic fragments, deletion fragments and in particular, fragments of FVIII polypeptides which exhibit functional biological activity. Variants of FVIII polypeptides of the present invention include fragments as described above, and also polypeptides with altered amino acid sequences due to amino acid substitutions, deletions, or insertions. Variants may occur naturally, such as an allelic variant. By an "allelic variant" is intended alternate forms of a gene occupying a given locus on a chromosome or genome of an organism or virus. Genes II, Lewin, B., ed., John Wiley & Sons, New York (1985), which is incorporated herein by reference. Variant polypeptides may comprise conservative or non-conservative amino acid substitutions, deletions or additions. Derivatives of FVIII polypeptides of the present invention, include polypeptides which have been altered so as to exhibit, for example, additional features not found in the native polypeptide. Examples include fusion proteins. An analog is another form of a FVIII polypeptide of the present invention. An example is a proprotein which can be activated by cleavage of the proprotein to produce an active mature polypeptide.

[0038] As used herein, the term "vector" refers to a construct made up of genetic material (i.e., nucleic acids). Typically the vector may be a plasmid which may contain an origin of replication which is functional in bacterial host cells, e.g., Eschericha coli, and selectable markers for detecting bacterial host cells comprising the plasmid. Plasmids of the present invention may include genetic elements as described herein arranged such that an inserted coding sequence can be transcribed and translated in eukaryotic cells. Also, while the plasmid may include a sequence from a viral nucleic acid, such viral sequences normally do not cause the incorporation of the plasmid into a viral particle, and the plasmid is therefore a non-viral vector. In certain embodiments described herein, a plasmid is a closed circular DNA molecule.

[0039] The term "expression" generally refers to the biological production of a product encoded by a coding sequence. In most cases a DNA sequence, including the coding sequence, is transcribed to form a messenger-RNA (mRNA). The messenger-RNA is translated to form a polypeptide product which has a relevant biological activity. Also, the process of expression may involve further processing steps to the RNA product of transcription, such as splicing to remove introns, and/or post-translational processing of a polypeptide product.

[0040] As used herein, the term "polypeptide" is intended to encompass a singular "polypeptide" as well as plural "polypeptides," and comprises any chain or chains of two or more amino acids. Thus, as used herein, terms including, but not limited to "peptide, "protein," "amino acid chain," or any other term used to refer to a chain or chains of two or more amino acids, are included in the definition of a "polypeptide," and the term "polypeptide" may be used instead of, or interchangeably with any of these terms. The term further includes polypeptides which have undergone post-translational modifications, for example, glycosylation, acetylation, phosphorylation, amidation, derivatization by known protecting/blocking groups, proteolytic cleavage, or modification by non-naturally occurring amino acids.

[0041] Also included as polypeptides of the present invention are fragments, derivatives, analogs, or variants of the foregoing polypeptides, and any combination thereof. Polypeptides, and fragments, derivatives, analogs, or variants thereof of the present invention can be biologically functional polypeptides related to FVIII polypeptides, which are used to prevent or treat, i.e., cure, ameliorate, lessen the severity of, or prevent or reduce Haemophilia A.

[0042] "Codon optimisation" is defined as modifying a nucleic acid sequence for enhanced expression in the cells of the mammal of interest, e.g. hamster, by replacing at least one, more than one, or a significant number, of codons of the native sequence with codons that are more frequently or most frequently used in the genes of that mammal or cell type. Various species and cell types exhibit particular bias for certain codons of a particular amino acid.

[0043] Many organisms display a bias for use of particular codons to code for insertion of a particular amino acid in a growing peptide chain. Codon preference or codon bias, differences in codon usage between organisms, is afforded by degeneracy of the genetic code, and is well documented among many organisms. Codon bias often correlates with the efficiency of translation of messenger RNA (mRNA), which is in turn believed to be dependent on, inter alia, the properties of the codons being translated and the availability of particular transfer RNA (tRNA) molecules. The predominance of selected tRNAs in a cell is generally a reflection of the codons used most frequently in peptide synthesis. Accordingly, genes can be tailored for optimal gene expression in a given organism based on codon optimization.

[0044] Given the large number of gene sequences available for a wide variety of animal, plant and microbial species, it is possible to calculate the relative frequencies of codon usage. Codon usage tables are readily available, for example, at the "Codon Usage Database" available at www.kazusa.or.jp/codon/ (visited 19^th February 2013), and these tables can be adapted in a number of ways. See Nakamura (20). The codon usage table for human, calculated from GenBank , Flat File Release 160.0 [June 15 2007]. These tables use mRNA nomenclature, and so instead of thymine (T) which is found in DNA, the tables use uracil (U) which is found in RNA. The tables have been adapted so that frequencies are calculated for each amino acid, rather than for all 64 codons.

[0045] By utilising these or similar tables, one of ordinary skill in the art can apply the frequencies to any given polypeptide sequence, and produce a nucleic acid fragment of a codon optimised coding region which encodes the polypeptide, but which uses codons more optimal for a given species. Codon optimised coding regions can be designed by various different methods.

[0046] In one method, termed "uniform optimisation," a codon usage table is used to find the single most frequent codon used for any given amino acid, and that codon is used each time that particular amino acid appears in the polypeptide sequence. In another method, termed "full-optimization," the actual frequencies of the codons are distributed randomly throughout the coding region. Thus, using this method for optimization, if a hypothetical polypeptide sequence had 100 leucine residues, referring to frequency of usage in the humans, about 7, or 7% of the leucine codons would be UUA, about 13, or 13% of the leucine codons would be UUG, about 13, or 13% of the leucine codons would be CUU, about 20, or 20% of the leucine codons would be CUC, about 7, or 7% of the leucine codons would be CUA, and about 41, or 41% of the leucine codons would be CUG. These frequencies would be distributed randomly throughout the leucine codons in the coding region encoding the hypothetical polypeptide. As will be understood by those of ordinary skill in the art, the distribution of codons in the sequence can vary significantly using this method, however, the sequence always encodes the same polypeptide.

[0047] In using the "full-optimisation" method, an entire polypeptide sequence, or fragment, variant, or derivative thereof is codon optimised by any of the methods described herein. Various desired fragments, variants or derivatives are designed, and each is then codon optimised individually. Alternatively, a full-length polypeptide sequence is codon optimised for a given species resulting in a codon optimised coding region encoding the entire polypeptide, and then nucleic acid fragments of the codon optimised coding region, which encode fragments, variants, and derivatives of the polypeptide are made from the original codon optimised coding region. As would be well understood by those of ordinary skill in the art, if codons have been randomly assigned to the full-length coding region based on their frequency of use in a given species, nucleic acid fragments encoding fragments, variants, and derivatives would not necessarily be fully codon optimised for the given species. However, such sequences are still much closer to the codon usage of the desired species than the native codon usage. The advantage of this approach is that synthesizing codon optimised nucleic acid fragments encoding each fragment, variant, and derivative of a given polypeptide, although routine, would be time consuming and would result in significant expense.

[0048] As well as in vitro applications in order to produce industrial quantities of rFVIII and variants thereof, such as B domain deleted versions for use in therapy, the present invention may also be applied to expression of rFVIII as described herein in vivo for potential gene therapy application in haemophilia patients.

Detailed Description

[0049] The present invention will now be further described by way of example and with reference to the figures that show:

Figure 1 (also see SEQ ID NO:3) shows a preferred FVIII B-domain deleted amino acid sequence for use in the present invention;

Figure 2 (also see SEQ ID NO:1) shows a codon optimised nucleic acid encoding the FVIII B-domain deleted amino acid sequence shown in Figure 1, for expression in hamster; and

Figure 3: (a - f) shows the results of experiments concerning cell viability following expression of FVIII alone and in conjunction with VWF. CHO DG44 cells were transfected with the DNA constructs indicated. The percent cell viability of the transfected cells is shown and the control no DNA transfection is shown. Selection (G418 or zeocin) was initiated 48 h after transfection.

Examples

Introduction

[0050] CHO DG44 cell line is a dihydrofoate reductase (DHFR)-deficient cell line adapted to growth as a suspension culture. p571_BDDFVIIIcoop is an expression vector (11) containing expression cassettes for the Neo gene conferring resistance to the antibiotic geneticin (G418); DHFR allowing DHFR^- cells to grow in the absence of hypoxanthine and thymidine; and BDDFVIIIcoop allowing the expression of human B-domain deleted human FVIII. We have previously transfected CHO cells with the same vector containing non-codon optimised HFVIII and HBDDFVIII sequences and repeatedly obtained stably transfected clonal cell lines, albeit with poor expression characteristics (unpublished and 12, 13). pcDNA3.1Zeo_VWFcoop is based on the expression vector containing expression cassettes for the Zeo gene conferring resistance to the antibiotic Zeocin http://www.lifetechnologies.com/1/1/10790-pcdna3-1-zeo-mammalian-expression-vector.html and VWFcoop allowing the expression of human VWF.

Methods and Materials

DNA constructs

[0051] DNA sequences codon optimised for expression in hamster cells encoding human BDDFVIII and VWF were generated by analysis of the BDDFVIII SQ cDNA sequence (Sanberg et al (22)) and the VWF reference sequence (NP_000543.2) and adaption of the codon usage to the bias of Cricetulus griseus using codon adaptation index performed by GeneArt (GeneArt AG) using their in-house proprietary software GeneOptimizer. The nucleic acid sequence of codon optimised versions of human BDD FVIII and VWF for expression in CHO cells are identified in SEQ ID NOs: 1 and 2 respectively. The corresponding amino acid sequences for BDD FVIII and VWF are shown in SEQ ID NOS: 3 and 4 respectively. Optimisation also removed cis-acting sequence motifs, including internal TATA-boxes, chi-sites and ribosomal entry sites, AT- or GC-rich sequence stretches, AU-rich elements, inhibitory and cis-acting repressor sequence elements, repeat sequences, RNA secondary structures, and all cryptic splice sites. The optimised genes BDDFVIIIcoop and VWFcoop were synthesised and cloned into the plasmids p571 (pNeoIG502; Kemball-Cook et al (11) respectively. Each construct was fully sequenced prior to use (Source BioScience UK Ltd).

Transfection and selection of CHO cells

[0052] CHO DG44 cells were purchased from Life Technologies. The cells were maintained in CD DG44 media supplemented with 8 mmol/L glutamine and 0.1% pluronic F-68 (Life Technologies) at 37°C, 5% CO₂ on an orbital shaker (120 rpm). CHO DG44 cells with a viability >95% were used in all transfections. 18 µg of linearised plasmid DNA was used in each transfection. The cells were transfected with the FreeStyle MAX reagent according to the manufacturer's instructions (Life Technologies). Briefly, 18µL of plasmid DNA and 15µL of FreeStyle MAX reagent in OptiPRO SFM media was incubated for 10 minutes at room temperature to allow the formation of DNA-lipid complexes. The complex was then transferred to a 125mL flask containing 30mL of cells (0.5 x 10⁶ cells/mL) and incubated in a 37°C, 5% CO₂ incubator on an orbital shaker (120 rpm). 48 hours after transfection either G418 (250µg/mL) or zeocin (200µg/mL) was added to the culture to select for BDDFVIIIcoop or VWFcoop respectively. Cell counts (total and non-viable) were performed every 3-4 days using a Nucleocounter according to the manufacturer's instructions (Sartorius Stedim).

PCR analysis

[0053] Cells were analysed by PCR using oligonucleotide primers designed to amplify amplicons generating overlapping fragments across the entire coding sequences and the vector cDNA junctions. Briefly, 100 µL of cells (2.97 x 10⁵ cells) were harvested by centrifugation and resuspended in 75 µL of alkaline lysis reagent (25 mM NaOH, 0.2 mM EDTA pH 12), and incubated at 95 °C for 30 minutes before adding 75 µL of neutralizing reagent (40mM TRIS pH 5). PCR reactions were performed using 1 µL of the extracted DNA as template, PCR master mix (Promega), 1µmol/L 5' and 3' oligonucleotide primer pairs (Sigma Genosys) using the PCR program: 95 °C, 3 minutes; 95 °C, 30 seconds, 55 °C, 30 seconds, 72 °C 60 seconds repeated for 30 cycles and finally 72 °C, 10 minutes. PCR fragments were analysed by agarose gel electrophoresis.

Measurement of FVIII

[0054] The cofactor activity of media samples was assessed using the Biophen FVIII:C Chromagenic assay (Quadratech Diagnostics) as per the manufacturer's instructions. A standard curve was constructed by using 1:2 serial dilutions of a plasma calibrator (Biophen; Quadratech Diagnostics). Standards and samples were assayed in duplicate.

Results

[0055] CHO DG44 cells were transfected with linearised plasmid DNAs either (p571_BDDFVIIIcoop or pcDNA3.1Zeo_VWFcoop) and cultured for 48 hours, after which selection for stably transfected cells was initiated by the addition of appropriate antibiotic selection to (G418 (geneticin) for the BDDFVIIIcoop and zeocin for the VWFcoop). Cell counts were performed every 3-4 days to determine cell viability (Figure 3A).

[0056] CHO DG44 cells not transfected with the p571_BDDFVIIIcoop were sensitive to G418 and cell viability was zero after 14 days selection as predicted from the results of a G418 sensitivity test performed on non-transfected CHO DG44 cells. The majority of cells in the transfected cell culture with p571_BDDFVIIIcoop were also sensitive to G418 representing either non-transfected cells or cells in which no stable integration has occurred. In comparison with the non-transfected control cell viability of the p571_BDDFVIIIcoop transfected culture remained above zero suggesting the presence of stably transfected cells. However, by day 41 the cell viability dropped to zero (Figure 3A). This experiment was repeated a further two times and on both occasions a similar profile was observed (Figure 3B and 3C). No stable transfectants were obtained on each of these three occasions. DNA prepared from cells 38 days after transfection was positive by PCR for the p571_BDDFVIIIcoop sequence. Hence the CHO DG44 cells were successfully transfected with the expression vector as evidenced by resistance to G418 at a concentration that killed non-transfected cells and PCR positivity for the expression cassette. The failure to obtain stable viable transfectants was unexpected and may be due to the high level of expression of BDDFVIIIcoop leading to apoptosis. CHO DG44 cells not transfected with the pcDNA3.1Zeo_VWFcoop were sensitive to Zeocin and cell viability was zero after 14 days selection as predicted from the results of a Zeocin sensitivity test performed on non-transfected CHO DG44 cells. The majority of cells in the transfected cell culture with pcDNA3.1Zeo_VWFcoop were also sensitive to Zeocin representing either non-transfected cells or cells in which no stable integration has occurred. In comparison with the non-transfected control cell viability of the pcDNA3.1Zeo_VWFcoop transfected culture remained above zero suggesting the presence of stably transfected cells. The cell viability rapidly recovered and by 23 days after the transfection the culture was 97% viable (Figure 3D). Viable growing cultures of these cells were established and shown by PCR to contain the entire VWFcoop expression cassette.

[0057] The CHO DG44 cells stably transfected with pcDNA3.1Zeo_VWFcoop were then transfected with p571_BDDFVIIIcoop. CHO DG44 cells not transfected with the p571_BDDFVIIIcoop were sensitive to G418 and cell viability was zero after 15-17 days selection as predicted from the results of a G418 sensitivity test performed on non-transfected CHO DG44 cells. The majority of cells in the transfected cell culture with p571_BDDFVIIIcoop were also sensitive to G418 representing either non-transfected cells or cells in which no stable integration has occurred. In comparison with the non-transfected control cell and previous transfections of CHO DG44 with p571_BDDFVIIIcoop the CHO DG44_pcDNA3.1Zeo_VWFcoop culture transfected with p571_BDDFVIIIcoop remained above zero suggesting the presence of stably transfected cells. The cell viability rapidly recovered and by 27 days after transfection the culture was >97% viable (Figure 3E). This transfection was repeated and similar results obtained (Figure 3F). In both these cases viable growing cultures of these cells were established and shown by PCR to contain the entire BDDFVIIIcoop and VWFCOOP expression cassettes. These polyclonal cell populations were subsequently determined to be expressing an average level of 0.003pg/cell/day prior to methotrexate amplification. Activity levels of produced material were also analysed (using the FVIII:C chromogenic assay and Plasma calibrator from Biophen) revealing that the majority of produced material was biologically active.

[0058] These polyclonal cells were then subjected to a clonal selection procedure consisting of :

• Preparing a 30 mL culture of cells to a cell count of 1 x 10⁶ cells/mL.
• Diluting the cells by serial 10-fold dilution to a concentration of < 0.05 cells/mL in complete OptiCHO media (LifeTech).
• Plating 0.2 mL of these cells in sterile 96-Well Edge Plates, (Thermo Scientific Nunc)
• Medium evaporation from the perimeter wells of a microtitre plate is a significant problem, especially when the cells are grown for >3 days. As the medium evaporates over time (even in a humidified environment) the concentration of media components changes, influencing cell growth and performance. A traditional approach to this problem has been to fill the perimeter wells with sterile water or PBS. An alternative is the use of Nunc Edge 96-well plates, which have a reservoir surrounding the outer area of the plate that can be filled with sterile water, preventing evaporation from the inner wells. In this case all 96 wells can be used.
• Plates were then incubated undisturbed for 10-14 days in a 37 °C, 5% CO2 incubator with no shaking.
• Growing cells were transferred from the 96-well plates to 24-well plates by pipetting the cells up and down gently and transferring the entire contents of one well to a single well of a 24-well plate containing 1 mL of fresh complete OptiCHO media
• Media was then assayed for FVIII antigen and activity by standard procedures.
• mycoplasma testing was undertaken throughout.

[0059] This procedure resulted in the isolation of three cell lines expressing rhFVIII at 0.03-4pg/cell/day.

[0060] Polyclonal populations of cells derived from this process were then subjected to methotrexate amplification (starting at 0.2µM MTX and increasing by 0.1µM at each stage) to increase the copy number of the rhFVIII expression cassette. Cell productivity was assayed throughout by the above means. Cells amplified to a level of 0.5µM MTX increased productivity of rhFVIII. Beyond this level of MTX, rhFVIII fell dramatically. Polyclonal cells derived from this stage expressed rhFVIII at ≥0.1 pg/cell/day.

[0061] These polyclonal cells can be subjected to a clonal selection procedure as described above. This will result in the isolation of cell lines expressing rhFVIII at an increased rate of perhaps 0.3-0.4 pg/cell/day.

REFERENCES

[0062] 

1. Zhang et al Nat. Genet. (2003) 34: 220-225

2. Zhang et al J. Biol. Chem. (2005) 280: 25881-25886

3. Pipe, Haemophilia (2009) 15:1187-1196

4. Pittman, et al Blood (1994) 84: 4214-4225

5. Malhotra et al, Proc. Natl. Acad. Sci. USA (2008) 105: 18525-18530

6. Kaufman et al, J. Biol. Chem. (1988) 263: 6352-6362 and USJ, 198, 349

7. Miao et al, Blood (2004) 103: 3412-3419

8. Ward et al,,Blood (2011) 117:798-807

9. Marin, Biotechnol J. (2008) 3: 1047-1057

10. Tsai et al, J. Mol. Biol. (2008) 383: 281-291

11. Kemball-Cook et al, Gene (1994) 139: 275-279

12. David et a,l J Thromb Haemost (2003) 1: 139-146

13. David et al, B.J. Haem. (2001)113;604-615

14. Wise et al, JBiolChem (1991)266, 21948-21955

15. Kolind et al, JBiotec (2011) 151, 357-362)

16. Spencer et al, Molecular Therapy (2011), 19/2, 302-309.

17. Kaufman and Sharp, J. Mol. Biol. (1982)159, 601-621)

18. Lorimer D, Raymond A, Walchli J, Mixon M, Barrow A, Wallace E, Grice R, Burgin A, Stewart L., BMC Biotechnol. 2009 9:36)

19. Bowie, et al., "Deciphering the Message in Protein Sequences: Tolerance to Amino Acid Substitutions," Science 247:1306-1310 (1990).

20. Nakamura, Y., et al. "Codon usage tabulated from the international DNA sequence databases: status for the year 2000" Nucl. Acids Res. 28:292 (2000).

21. Davis LGG et al., Basic Methods in Molecular Biology, (2nd Ed., McGraw-Hill, 1995).

22. Sanberg et al (2001) Thromb Haemost 85, 93-100.

SEQUENCE MISTING

[0063] 

<110> Profactor Pharma Ltd

<120> Recombinant Protein

<130> PE955669WO

<150> GB1304973.9
<151> 2013-03-19

<160> 4

<170> PatentIn version 3.5

<210> 1
<211> 4377
<212> DNA
<213> Artificial Sequence

<220>
<223> codon optimised B domain deleted F VIII sequence for expression in CHO cells

<400> 1

<210> 2
<211> 8445
<212> DNA
<213> Artificial Sequence

<220>
<223> codon optimised VWF sequence for CHO expression

<400> 2

<210> 3
<211> 1457
<212> PRT
<213> Homo sapiens

<400> 3

<210> 4
<211> 2813
<212> PRT
<213> Homo sapiens

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Claims

1. A mammalian cell comprising an exogenously introduced nucleic acid which is capable of recombinantly expressing FVIII wherein the nucleic acid, or portion thereof which encodes said FVIII has been codon optimised for expression by the mammalian cell; and wherein the cell further recombinantly co-expresses von Willebrand Factor (VWF).

2. The mammalian cell according to claim 1 wherein the nucleic acid encoding the VWF has also been codon optimised for expression by the mammalian cell.

3. The mammalian cell according to claims 1 or 2 wherein the mammalian FVIII is human FVIII or a B domain deleted version of human FVIII.

4. The mammalian cell according to any preceding claim wherein the cell is a 293, CHO, 3T3, BHK, MICK, Vero, Junket, or HeLa cell, as well as derivatives of such cells known in the art.

5. The mammalian cell according to any preceding claim wherein the mammalian FVIII is human FVIII or a B domain deleted version of human FVIII codon optimised for hamster and the mammalian cell is a CHO or BHK cell.

6. The mammalian cell according to any of claims 3-5 wherein the FVIII amino acid sequence is a FVIII sequence from which the B domain has been deleted, and optionally replaced with a short B-domain spacer rich in asparagine-linked oligosaccharides.

7. The mammalian cell according to any preceding claim wherein the FVIII amino acid sequence is the sequence shown in SEQ ID NO:1.

8. The mammalian cell according to any preceding claim wherein the nucleic acid sequence encoding the mammalian FVIII is at least 90%, 95%, 96%, 97%, 98% 99%, or is identical to the sequence is shown in SEQ ID NO:3.

9. The mammalian cell according to any preceding claim wherein the VWF amino acid sequence is the sequence shown in SEQ ID NO:2.

10. The mammalian cell according to any preceding claim wherein the VWF amino acid sequence is the sequence shown in SEQ ID NO:4.

11. A cell culture comprising a mammalian cell according to any preceding claim, which is capable of expressing the FVIII in an amount of ≥ 0.1pg/cell/day, typically ≥ 0.25 pg/cell/day.

12. A method of preparing recombinant mammalian FVIII or a B domain deleted version of FVIII, comprising providing a cell, transfecting the cell with a vector capable of recombinantly expressing VWF and thereafter further transfecting cells transfected with VWF with a vector capable of recombinantly expressing FVIII or a B domain deleted version of FVIII, wherein the transfections are carried out with vectors which comprise codon optimised nucleic acid constructs capable of expressing FVIII or a B domain deleted version of FVIII and VWF in said cell.

13. The method according to claim 12 comprising adding methotrexate to the cell culture medium, at a concentration up to 0.5µM.

14. The method according to any of claims 12-13 further comprising purifying FVIII or a B domain deleted version of FVIII or complex comprising FVIII or a B domain deleted version of FVIII from the cell and/or culture medium in which the cell is grown.

Ansprüche

1. Säugetierzelle, umfassend eine exogen eingeführte Nucleinsäure, die in der Lage ist, FVIII rekombinant zu exprimieren, wobei die Nucleinsäure oder ein Teil von ihr, der das FVIII codiert, für die Expression durch die Säugetierzelle Codon-optimiert wurde; und wobei die Zelle ferner Von Willebrand-Faktor (VWF) co-exprimiert.

2. Säugertierzelle nach Anspruch 1, wobei die Nucleinsäure, die den VWF codiert, ebenfalls für die Expression durch die Säugetierzelle Codon-optimiert wurde.

3. Säugetierzelle nach Anspruch 1 oder 2, wobei der Säugetier-FVIII ein humaner FVIII oder eine B-Domäne-deletierte Version von humanem FVIII ist.

4. Säugetierzelle nach einem der vorhergehenden Ansprüche, wobei die Zelle eine 293-, CHO-, 3T3-, BHK-, MICK-, Vero-, Junket- oder HeLa-Zelle sowie Derivate derartiger auf dem Fachgebiet bekannter Zellen ist.

5. Säugetierzelle nach einem der vorhergehenden Ansprüche, wobei der Säugetier-FVIII ein humaner FVIII ist oder eine B-Domänen-deletierte Version von humanem FVIII Codon-optimiert für Hamster, und die Säugetierzelle eine CHO- oder BHK-Zelle ist.

6. Säugetierzelle nach einem der Ansprüche 3 bis 5, wobei die FVIII-Aminosäuresequenz eine FVIII-Sequenz ist, von der die B-Domäne deletiert worden ist und wahlweise durch einen kurzen B-Domänen-Spacer ersetzt wurde, der reich an Asparagin-verknüpften Oligosacchariden ist.

7. Säugetierzelle nach einem der vorhergehenden Ansprüche, wobei die FVIII-Aminosäuresequenz die in SEQ ID NO: 1 gezeigte Sequenz ist.

8. Säugetierzelle nach einem der vorhergehenden Ansprüche, wobei die Nucleinsäuresequenz, die den Säugetier-FVIII codiert, zu mindestens 90%, 95%, 96%, 97%, 98%, 99% oder identisch ist mit der Sequenz, die in SEQ ID NO: 3 gezeigt ist.

9. Säugetierzelle nach einem der vorhergehenden Ansprüche, wobei die VWF-Aminosäuresequenz die in SEQ ID NO: 2 gezeigte Sequenz ist.

10. Säugetierzelle nach einem der vorhergehenden Ansprüche, wobei die VWF-Aminosäuresequenz die in SEQ ID NO: 4 gezeigte Sequenz ist.

11. Zellkultur, umfassend eine Säugetierzelle nach einem der vorhergehenden Ansprüche, die in der Lage ist, den FVIII in einer Menge von >0,1 pg/Zelle/Tag, im typischen Fall >0,25 pg/Zelle/Tag, zu exprimieren.

12. Verfahren zur Herstellung von rekombinantem Säuger-FVIII oder einer B-Domäne-deletierten Version von FVIII, umfassend das Bereitstellen einer Zelle, Transfektieren der Zelle mit einem Vektor, der zum rekombinanten Exprimieren von VWF in der Lage ist, und danach weiteres Transfektieren von Zellen, die mit VFIII transfiziert sind mit einem Vektor, der zum rekombinanten Exprimieren von VFIII in der Lage ist oder einer B-Domäne-deletierten Version von FVIII, wobei die Transfektionen mit Vektoren ausgeführt werden, die Codon-optimierte Nucleinsäure-Konstrukte aufweisen, die zum Exprimieren von FVIII oder einer B-Domäne-deletierten Version von FVIII und VWF in der Zelle in der Lage sind.

13. Verfahren nach Anspruch 12, umfassend die Zugabe von Methotrexat zu dem Zellkulturmedium in einer Konzentration von bis zu 0,5 µl.

14. Verfahren nach einem der Ansprüche 12 bis 13, ferner umfassend das Reinigen von FVIII oder einer B-Domäne-deletierten Version von FVIII oder einem Komplex, der FVIII oder eine B-Domäne-deletierte Version von FVIII aus der Zelle und/oder dem Kulturmedium aufweist, in dem die Zelle aufgezogen worden ist.

Revendications

1. Cellule mammifère comprenant un acide nucléique introduit de façon exogène qui est capable d'exprimer par recombinaison FVIII, où l'acide nucléique, ou une portion de celui-ci, qui code pour ledit FVIII a été optimisé sur les codons pour une expression par la cellule mammifère; et où la cellule en outre co-exprime par recombinaison le facteur de von Willebrand (VWF).

2. Cellule mammifère selon la revendication 1, dans laquelle l'acide nucléique codant pour le VWF a été également optimisé sur les codons pour une expression par la cellule mammifère.

3. Cellule mammifère selon les revendications 1 ou 2, dans laquelle le FVIII mammifère est un FVIII humain ou une version à domaine B délété d'un FVIII humain.

4. Cellule mammifère selon l'une quelconque des revendications précédentes, où la cellule est une cellule 293, CHO, 3T3, BHK, MICK, Vero, Junket ou HeLa, aussi bien que des dérivés de ces cellules connus de la technique.

5. Cellule mammifère selon l'une quelconque des revendications précédentes, dans laquelle le FVIII mammifère est un FVIII humain ou une version à domaine B délété d'un FVIII humain à codons optimisés pour un hamster et la cellule mammifère est une cellule CHO ou BHK.

6. Cellule mammifère selon l'une quelconque des revendications 3-5, dans laquelle la séquence d'acides aminés de FVIII est une séquence de FVIII à partir de laquelle le domaine B a été délété et optionnellement remplacé avec un espaceur de domaine B court riche en oligosaccharides liés à une asparagine.

7. Cellule mammifère selon l'une quelconque des revendications précédentes, dans laquelle la séquence d'acides aminés de FVIII est la séquence montrée dans la SEQ ID NO: 1.

8. Cellule mammifère selon l'une quelconque des revendications précédentes, dans laquelle la séquence d'acide nucléique codant pour le FVIII mammifère est au moins 90%, 95%, 96%, 97%, 98%, 99% ou est identique à la séquence montrée dans la SEQ ID NO:3.

9. Cellule mammifère selon l'une quelconque des revendications précédentes, dans laquelle la séquence d'acides aminés de VWF est la séquence montrée dans la SEQ ID NO:2.

10. Cellule mammifère selon l'une quelconque des revendications précédentes, dans laquelle la séquence d'acides aminés de VWF est la séquence montrée dans la SEQ ID NO:4.

11. Culture cellulaire comprenant une cellule mammifère selon l'une quelconque des revendications précédentes, qui est capable d'exprimer le FVIII dans une quantité ≥ 0,1 pg/cellule/jour, typiquement ≥ 0,25 pg/cellule/jour.

12. Méthode pour la préparation d'un FVIII mammifère recombinant ou d'une version à domaine B délété de FVIII, comprenant la fourniture d'une cellule, la transfection de la cellule avec un vecteur capable d'exprimer par recombinaison VWF et par la suite en outre la transfection des cellules transfectées avec VWF avec un vecteur capable d'exprimer par recombinaison FVIII ou une version à domaine B délété de FVIII, dans laquelle les transfections sont réalisées avec des vecteurs qui comprennent des constructions d'acides nucléiques à codons optimisés capables d'exprimer FVIII ou une version à domaine délété B de FVIII et VWF dans ladite cellule.

13. Méthode selon la revendication 12, comprenant l'ajout de méthotrexate au milieu de culture cellulaire, à une concentration jusqu'à 0,5 µm.

14. Méthode selon l'une quelconque des revendications 12-13, comprenant en outre la purification de FVIII ou d'une version à domaine B délété de FVIII ou d'un complexe comprenant FVIII ou une version à domaine B délété de FVIII à partir de la cellule et/ou du milieu de culture dans lequel la cellule est mise à croître.

Drawing